Process of simultaneously spinning, twisting, and purifying rayon



March 20, 1934. I SANDERS ET AL 1,951,845

PROCESS OF SIMULTANEOUSLY SPINNING, TWISTING, AND PURIFYING RAYON Filed Nov. 1, 1930 gwoan iow Marshall I Sanders Ralph A .HaZes,

Patented Mar. 20, 1934 UNETED STATES PATENT OFFICE PROCESS OF SIMULTANEOUSLY SPINNING, TWISTING, AND PURIFYING RAYON Marshall T. Sanders,

Wilmington, Del., and

Application November 1, 1930, Serial No. 492.829

1 Claim.

This invention relates to the manufacture of rayon by the pot spinning process. It comprises combining the spinning and twisting operation with the subsequent operation of purifying the spun thread. The objects of the invention are to produce a rayon which will have (1) a uniform dye absorbing power throughout its length, (2) an increased elongation at the breakpoint, (3) less denier diiierence between the thread at the two ends of the pot cake; and to cheapen the cost of manufacture by (4) combining the operations of setting, twisting and purifying the thread, and (5) by collecting a greater yardage of thread in the spin pot of given size, thus reducing the labor required to dofi the cakes by increasing the time between doiis. I

We will describe the invention as it relates to the cuprammonium process when using an alkaline setting bath. It will be obvious to those skilled in the art that the process can also be used advantageously in those other rayon processes in which the thread requires a purifying treat ment after the spinningand twisting operation.

Heretoiore, it has been customary to spin cuprammonium cellulose solution into an alkaline setting bath and collect the precipitated thread on bobbins'or in spin pots. This set or precipitated thread still contains copper and ammonia which must be removed in a subsequent treatment with a liquid (usually dilute sulphuric acid) capable of removing them from the thread. This decopperizing operation is usually performed by unwinding the set thread from the bobbin or pot and collecting it on a bobbin or swift which rotates, partially submerged, in a bath of dilute acid. The thread is thensubjected to the washing, finishing, drying and packaging operations. In the case of bobbin spun thread, a twisting operation usually follows that of drying.

According to the process of this invention the set thread is conveyed from the setting bath and is fed into a spin pot in the usual manner.

One embodiment of the invention is illustrated in the accompanying drawing. The embodiment of the invention illustrated relates to the cuprammonium process. The cuprammonium solution of cellulose is spun into a setting bath 5 comprising a caustic soda solution. The set thread 6 is conducted over a godet wheel 7, through a funnel 8 and into a spin pot 9. The funnel and spin pot are co-axial and reciprocate relative to each other in the direction of their axes. The means for reciprocating the parts are not illustrated, for this forms no part of the invention. A spray nozzle 10 is attached to the funnel and so directed that it sprays dilute sulphuric acid against the face of the cake of thread as the thread collects in the spin pot. In this manner the thread is collected, twistedand decopperized simultaneously. If the alkaline precipitating bath be of such composition that somecopper hydrate tends 'to collect in the funnel, we may flow a small quantity of dilute acid into the funnel along with the thread. By the process of this invention we obviate the difiiculties inherent in the old processes. In the old processes the set thread is continually washed with the setting bath, carried to' the pot or bobbin by the set thread. This alkaline bath has a slight solvent action on the copper contained in the thread' Thus the oldest thread collected will contain less copper per unit of cellulose than the youngest thread. Furthermore, water and ammonia are gradually lost by the thread, and the quantity of these, per unit of cellulosevaries with the age of the thread. To obtain thread of uniform dye absorption, the amounts of the various constituents of the set thread, per unit of cellulose, must be constant, and the composition of the decopperizing bath must be constant. These conditions are achieved by the processof the invention.

The elongation, at the break point, of the finished rayon is influenced by the tension or the degree of stretching to which the thread is subjected at the instant of decopperization. During this period the thread momentarily becomes easily elongated by even small amounts of tension. The more the thread is elongated during the period of decopperizing, the less the elongation at the break point of the finished rayon. In old processes where the thread is pulled through the acid bath, it is subjected to appreciable tension by the drag of the thread through the bath and over the various guides. In the process of this invention, the set, undecopperized thread is laid against the cake of already decopperized thread in the spin pot, and being thus supported, is not elongated during the period of decopperization.

We have observed that under the old methods of manufacture, especially when collecting set, undecopperized thread in a pot, that the denier of the thread at the outside of the cake is usually less than that at the inside of the cake. We have also observed that the thread made according to the new process shows no appreciable denier difference between the two ends of the cake. The set, undecopperized thread is much more bulky than-the decopperized thread. This enables one to collect several times the amount of decopperized thread than undecopperized thread in a cake of a given volume. Our experience has been that we can collect approximately four times as much decopperized thread as undecopperized thread in a cake of given volume. This enables one to spin four times as much thread in a pot, as previously, before it becomes necessary to change spin pots. The economic advantages in the reduction of labor through this effect are obvious. The combining of the decopperizing with the spinning operation eifects economies through the saving of the cost of decopperizing machines and the labor necessary for their operation.

It is obvious that the compositions of the cellulose solution, the setting bath, andthe decopperizing acid, also the length of thread in the setting bath, the relative locations of the parts of the machine, etc., may be varied to suit the local conditions and the denier of the thread being spun, without departing from the scope of the invention.

In one embodiment of this invention we spun a cuprammonium solution containing 3.6% cellulose, 1.5% of copper and 4.3% of ammonia into a setting bath containing grams of NaOI-I per liter. The resultant thread (of 100 denier size) was collected in a spin pot and simultaneously sprayed with 340 cubic centimeters per minute, of 20 grams per liter sulphuric acid. The finished rayon had a uniform dye absorbing power throughout its length, was of even denier, had excellent elongation and high strength.

It is within the skill of those versed in the art to change the proportions and quantities of the materials and the conditions of operation to produce any desired properties in the finished rayon. We have used as precipitating or setting baths, solutions of caustic soda up to four hundred grams per liter concentration. We can use decopperizing acid of from, say, five grams to 300 or 4510 grams per liter strength. It is obvious that the rate of flow of the acid will depend to some extent on its concentration, as the decopperizing; should be complete.

After the requisite amount of thread has been collected on the pot and the decopperization is complete, the thread may be given the usual washing, bleaching and finishing treatments.

The thread is then dried and packaged. While we prefer to wash the decopperized thread in the cake form, yet it may be skeined and then washed. The treatment of the yarn subsequent to decopperization is no part of the invention covered by this application. The adaptation of this invention to other rayon processes is within the skill of those versed in the art. For example, in the viscose process, the thread may be simultaneously spun and desulphurized; in the nitro process the thread may be collected in the pot and simultaneously denitrated.

This invention relates, broadly, to the carrying on, simultaneously, of the operations of spinning and purifying the spun thread. The purifying liquid may be introduced into the pot in any suitable manner. For example, it might all be entered through the funnel, or the pot might be permanently attached to a hollow driving shaft; the thread may be collected in a removable inner liner, and the purifying solution may be fed into the pot through the hollow driving shaft and then be distributed over the face of the cake. We are familiar with the fact that in one copper-ammonia process the thread is set in an alkaline bath, pulled through an acid bath and then wound on a swift rotating partially submerged in a bath of acid. This process differs from ours in two important particulars,(1) the thread is under appreoiable tension while being decopperized, and (2) the thread is collected in an untwisted condition and must be subsequently twisted.

Having described our invention, what we claim is:

The herein described process of manufacturing rayon by the cuprammonium process which includes the step of collecting an alkali precipitated spun thread in a cake in a centrifuge wherein the thread is uniformly supported against tension and elongation while simultaneously discharging upon said cake and uniformly throughout the height thereof wholly within the said centrifuge,- 

